HOW TO TEST THE THERMAL CONDUCTIVITY OF GRAPHITE SHEET?

With the upgrading of electronic products, a variety of high integrated and high-performance mini electronic equipment are constantly born. At the same time, the demand of heat dissipation management is also growing. Pyrolytic graphite sheet has been widely used in many fields such as electronics, communication, lighting, aviation, national defense and military industry.

So, how to test the thermal conductivity of graphite sheet?

Dasen is using NETZSCH LFA447 thermal conductivity meter to test the horizontal thermal conductivity of graphite sheet. When a laser pulse irradiates the center of the bottom surface of the sample, the heat of the sample propagates along the plane direction of the sample from the center of the bottom surface, and also propagates upward. At this time, the thermal diffusion coefficient in the plane direction of the sample can be obtained by detecting the temperature rise at a certain radius on the upper surface of the sample. The thermal conductivity of the sample in the plane direction can be obtained by multiplying the specific heat and density of the sample.

In practical use, it is found that after the first test, if the same sample graphite sheet is not taken out, but directly tested for the second time. The thermal diffusivity will vary greatly, which is a common occurrence.

NETZSCH technical engineer explained: this has something to do with the sample itself. Most of the graphite foil is not very smooth, with many folds and the surface is not very smooth. In this way, during the test, the heat path of heat conduction will change because of the existence of folds. The heat path of heat conduction is a comprehensive factor, not always fixed the same. Therefore, the thermal diffusion coefficient will be slightly different, and the calculated thermal diffusion coefficient of each hit point is different. Especially for the samples with many folds, the data error will increase correspondingly.